In This Article The Flynn Effect

  • Introduction
  • General Overviews
  • Practical Implications
  • The Twins and Factor X

Psychology The Flynn Effect
James R. Flynn
  • LAST REVIEWED: 08 May 2015
  • LAST MODIFIED: 30 January 2014
  • DOI: 10.1093/obo/9780199828340-0150


Until 1984, it was believed that IQ was relatively stable at least in developed nations. There had been reports of IQ gains among exotic groups, canal children in Britain, Tennessee mountain children, second-generation immigrants in Honolulu, but these seemed to be cases of extreme environments undergoing radical change. In 1948, Tuddenham compared US data from World War I and World War II and found about a full Standard Deviation (SD = 15 throughout) increase on US Army mental tests. Because he interpreted this as almost entirely due to extra years of schooling, it seemed to raise no problems about the theory of intelligence: the gains were dismissed as if they had been on academic achievement tests rather than intelligence tests. In 1982, Richard Lynn found gains on the WISC (Wechsler’s Intelligence Scale for Children) in Japan. That these had occurred in a developed nation should have posed the question: Could this be an international phenomenon? But at that time, there was a perception that the Japanese were unusual and that their gains merely underlined their superiority. However, in 1984, Flynn showed that Americans had also made massive gains: 14 IQ points over forty-six years (1932 to 1978). He emphasized that whether or not these were “intelligence” gains, they posed practical problems by acting as a confounding variable. The longer the time between when the test was normed and when it was administered, the more IQ scores were inflated. If you used a test normed on a representative sample from 1932, the general performance (and the norms they set) was much weaker than if you used a test based on a representative sample from 1972. Thanks to 12 IQ points gained over those forty years, a group of subjects merely average (mean 100) on the newer test would have a mean IQ of 112 on the older test. The inflation of IQs because of obsolete norms led to inflated estimates of the effects of intervention, adoption, and aging, and also misdiagnosis of whether individuals had met IQ cutting lines that affected everything from the administration of the death penalty to who should befit from special education. In 1987, Flynn showed that there had been massive IQ gains in fourteen developed nations on all sorts of tests, including those that were considered the “purest” measures of intelligence, such as Raven’s Progressive Matrices. These gains were too huge to identify with any commonsense notion of intelligence gains. For example, Dutch males had gained 20 IQ points on Raven’s between 1952 and 1982. Was the average member of the younger generation really brighter than 90 percent of his father’s generation? Or was it unfair to compare those who scored 80 (against current norms) without being exposed to modernity with those who today scored 80 after being exposed to modernity? The latter, if true, implied something important: modernity tends to confer cognitive skills that our ancestors lacked.

General Overviews

Any general overview of IQ gains will not only record the evidence for IQ gains in a variety of nations but also discuss all the problems that arise. Flynn 1987 was a first attempt but understandably posed problems without providing solutions. Neisser 1998 captures the reactions of the scholarly community. Jensen 1998 questions the real-world significance of the greater part of the gains by arguing that they did not correlate with g or the so-called general intelligence factor. Flynn 2009 replies to Jensen and argues that IQ gains signaled the occurrence of important events in the cognitive history of the 20th century. Fox and Mitchum 2013 covers much of the literature and draws its own conclusions. In 2013, a special issue of Intelligence is devoted to the “Flynn Effect,” and Flynn 2013 gives an overview of the most recent developments.

  • Flynn, J. R. 1987. Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin 101:171–191.

    DOI: 10.1037/0033-2909.101.2.171E-mail Citation »

    The original evidence that massive IQ gains occurred on all kinds of IQ tests throughout the developed world. Problems for the theory of intelligence are foreshadowed.

  • Flynn, J. R. 2009. What is intelligence? Beyond the Flynn Effect. Expanded ed. New York: Cambridge Univ. Press.

    E-mail Citation »

    Originally published in 2007. It contrasts the state of mind of Americans in 1900, fixated on the concrete world, with that of Americans today, who have learned to use logic on the abstract, take the hypothetical seriously, and classify. The thesis is that these new “habits of mind” allow them to cope with the modern world and that the relevant IQ tests have picked them up.

  • Flynn, J. R. 2013. The “Flynn Effect” and Flynn’s paradox. Intelligence 41.6: 851–857.

    DOI: 10.1016/j.intell.2013.06.014E-mail Citation »

    The journal Intelligence has devoted an issue to the Flynn Effect. Flynn comments on the latest research, which ranges from the role of test sophistication, to correlations with g (the general intelligence factor), to dysgenic reproduction, to the trend of IQ gaps between nations to diminish.

  • Fox, M. C., and A. L. Mitchum. 2013. A knowledge-based theory of rising scores on “culture-free” tests. Journal of Experimental Psychology: General 142.3: 979–1000.

    DOI: 10.1037/a0030155E-mail Citation »

    The focus is primarily on explaining why college students made large gains on Raven’s between two generations, but it addresses many of the issues that are relevant to the causes and implications of the gains.

  • Jensen, A. R. 1998. The g factor: The science of mental ability. Westport, CT: Praeger.

    E-mail Citation »

    Jensen’s book is a comprehensive treatment of all aspects of IQ testing. Whenever cited, the index should be used as a guide to specific topics. It is written for scholars, but the section on IQ gains is clear enough.

  • Neisser, U., ed. 1998. The rising curve. Long-term gains in IQ and related measures. Papers presented at a conference held in the spring of 1996 at Emory University. Washington, DC: American Psychological Association.

    DOI: 10.1037/10270-000E-mail Citation »

    Neisser’s collection represents the results of a symposium of scholars bewildered by the gains but groping their way toward solutions.

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